... and shortly after the deal was signed (and the projected profit added to the books), the contract was swapped out / "sold" to a subsidiary mostly owned by E

... and shortly after the deal was signed (and the projected profit added to the books), the contract was swapped out / "sold" to a subsidiary mostly owned by Enron, and selling this propped up the books even more. The associated debt was in the subsidiary, and thus didn't show up on the balance sheet.